Donald Trump at a speech in Detroit. REUTERS/Eric Thayer Donald Trump attempted to reframe the conversation around his presidential campaign by further outlining his existing plan to kick-start the economy.

In a wide-ranging speech in Detroit on Monday, the Republican presidential nominee noted the decline of the city's manufacturing, which he blamed on globalism.

"Detroit was once the economic envy of the world. The people of Detroit helped power America to its position of global dominance in the 20th century," Trump said. "But for many living in this city, that dream has long ago vanished."

He added: "When we abandoned the policy of America First, we started rebuilding other countries instead of our own. The skyscrapers went up in Beijing and in many other cities around the world while the factories and neighborhoods crumbled in Detroit."

Throughout a speech that lasted almost an hour, the real-estate magnate elaborated on on his four-point to reform the tax code, renegotiate international trade deals, introduce a moratorium on new federal government regulations, and roll back regulations on energy sources like coal and oil.

Trump criticized Democratic presidential nominee Hillary Clinton, citing a Washington Post article that noted Clinton did not fulfill a campaign promise to create hundreds of thousands of jobs in upstate New York. He attempted to cast himself as an agent of change.

"Our party has chosen to make new history by selecting a nominee from outside the rigged and corrupt system. The other party has reached backwards into the past to choose a nominee from yesterday — who offers only the rhetoric of yesterday and the policies of yesterday," Trump said. "There will be no change under Hillary Clinton — only four more years of Obama."

Trump also not so subtly attempted to assuage Republicans who are increasingly uneasy about his aggressive campaign style.

The Republican presidential nominee hat-tipped House Speaker Paul Ryan's plan to change the tax brackets. Last week, Trump ignited a firestorm of criticism within GOP ranks when he said he would not endorse Ryan — a position he reversed on Friday.

"My plan will reduce the current number of brackets from seven to three and dramatically streamline the process. We will work with House Republicans on this plan, using the same brackets they have proposed: 12, 25, and 33 percent," Trump said.

Trump's speech, which was repeatedly disrupted by protesters, comes as he has floundered in recent state and national polls following the Democratic National Convention last month. According to the RealClearPolitics average of national polls, Clinton leads Trump by 7 points.